SPATIAL HETEROGENEITY, MOBILITY AND ACCESS: THE CASE OF RANGE MANAGEMENT IN THE SAHEL

In this paper, we develop and calibrate a spatial and intertemporal bioeconomic model of livestock production to the West African Sahel region. The model is then used to investigate the effects of land heterogeneity, range scale, and access rights on long term management of rangeland in the Sahel.Livestock Production/Industries,

TROPHIC PORTFOLIOS IN MARINE FISHERIES: A STEP TOWARDS ECOSYSTEM MANAGEMENT

Marine ecologists warn that humans are "fishing down marine food webs." To explore the economic implications of this phenomenon, this paper applies portfolio theory to aggregate fisheries data. It poses two definitions of a sustainable mean-variance catch frontier. It computes a mean-variance frontier for catch using UNFAO historical fisheries data. Finally, the paper discusses the historical trend in inefficiency.Environmental Economics and Policy, Resource /Energy Economics and Policy,

NAVIGATING U.S. FISHERY MANAGEMENT INTO THE 21ST CENTURY

Resource /Energy Economics and Policy,

Evaluating the New Zealand Individual Transferable Quota Market for Fisheries Management

The New Zealand ITQ system is a dynamic institution that has had many refinements since its inception more than 15 years ago. Nonetheless, the basic tenets of the system - setting a total allowable catch and leaving the market to determine the most profitable allocation of fishing effort - have remained intact. This paper assesses the New Zealand system to identify areas of success and/or possible improvement or expansion within it. The reasons for doing so are to highlight beneficial features and to identify features of the New Zealand ITQ system that are relevant to other potential tradable permit markets. Beneficial features include simple standardized rules for quota definition and trading across species and areas; very few restrictions on quota trading and holding; relative stability in the rules over time; and low levels of government involvement in the trading process. We find evidence that supports the assertion that fishers behave in a reasonably rational fashion and that the markets are relatively efficient. We do not find major changes in participation in these fisheries as a result of the system. We find evidence that suggests that the ITQ system is improving the profitability of fisheries in New Zealand. In general the evidence thus far suggests that the market is operating in a reasonably efficient manner and is providing significant economic gains. These factors suggest that New Zealand would want to have non-economic justifications for any significant changes to the system.

An Approach to Ecosystem-Based Fishery Management

Marine scientists and policymakers are encouraging ecosystem-based fishery management (EBFM), but there is limited guidance on how to operationalize the concept. We adapt financial portfolio theory as a method for EBFM that accounts for species interdependencies, uncertainty, and sustainability constraints. Illustrating our method with routinely collected data available from the Chesapeake Bay, we demonstrate the gains from taking into account species variances and covariances in setting species total allowable catches. We find over the period from 1962–2003 that managers could have increased the revenues from fishing and reduced the variance by employing ecosystem frontiers in setting catch levels.ecosystem-based fishery management, portfolio, trophic modeling, precaution

Spatial Externalities and Vector-Borne Plant Diseases: Pierce’s Disease and the Blue-Green Sharpshooter in the Napa Valley

Pierce’s Disease (PD) is a bacterial disease that can kill grapevines over a span of one to three years. In this paper, we examine and model PD and vector control decisions made at the vineyard level in the Napa Valley in an effort to understand how the pest and disease affect individual growers, and to examine spatial externality issues and potential benefits from cooperation between adjacent vineyards. The model that we created adds to the literature by (a) treating grape vines as capital stocks that take time to reach bearing age and thus cannot be immediately replaced in the event of becoming diseased. We also (b) relax the assumption of an interior solution by examining the boundaries of parameter space for which winegrape growing is profitable and thus allowing growers to abandon land if it is not. We also explore (c) the effect of changing different policy parameters, such as PD control and vine replacement costs. Finally (d) we examine the potential benefits of cooperation between growers to manage vector populations, and determine that coordinated vector control could help riparian-adjacent growers to lessen grapevine losses and land abandonment, and thus to remain profitable in times of high PD pressure.Pierce’s Disease, winegrapes, perennial crop modeling, agricultural pests and diseases, optimal control theory, Crop Production/Industries, Production Economics, Resource /Energy Economics and Policy, Q12, Q24, C61,

The Benefits and Costs of Alternative Policies for the Management of Pierce's Disease: A Case Study of the Blue-Green Sharpshooter in the Napa Valley

Replaced with revised version of poster on 07/23/10.Production Economics, Resource /Energy Economics and Policy,

AN INTRODUCTION TO SPATIAL MODELING IN FISHERIES ECONOMICS

Resource /Energy Economics and Policy,

MULTISPECIES REVENUE FUNCTION ESTIMATION FOR NORTH PACIFIC GROUNDFISH FISHERIES

Multiproduct, multispecies revenue functions are estimated for the midwater and bottom-trawl pollock fisheries off Alaska. There are strong year and seasonal effects on coefficient estimates, and the technology is joint in outputs for each major operation type. The model is a step toward prediction of fishery regulatory effects.Resource /Energy Economics and Policy,

Optimal Investment to Enable Evolutionary Rescue

'Evolutionary rescue' is the potential for evolution to enable population persistence in a changing environment. Even with eventual rescue, evolutionary time lags can cause the population size to temporarily fall below a threshold susceptible to extinction. To reduce extinction risk given human-driven global change, conservation management can enhance populations through actions such as captive breeding. To quantify the optimal timing of, and indicators for engaging in, investment in temporary enhancement to enable evolutionary rescue, we construct a model of coupled demographic-genetic dynamics given a moving optimum. We assume 'decelerating change', as might be relevant to climate change, where the rate of environmental change initially exceeds a rate where evolutionary rescue is possible, but eventually slows. We analyze the optimal control path of an intervention to avoid the population size falling below a threshold susceptible to extinction, minimizing costs. We find that the optimal path of intervention initially increases as the population declines, then declines and ceases when the population growth rate becomes positive, which lags the stabilization in environmental change. In other words, the optimal strategy involves increasing investment even in the face of a declining population, and positive population growth could serve as a signal to end the intervention. In addition, a greater carrying capacity relative to the initial population size decreases the optimal intervention. Therefore, a one-time action to increase carrying capacity, such as habitat restoration, can reduce the amount and duration of longer-term investment in population enhancement, even if the population is initially lower than and declining away from the new carrying capacity